Str^m-Tejsen and Chislett 



Fig. 13 - Processing unit 



consist of reversing the polarity of the signals fed to integrator-condensers, 

 controlling the limits of integration, activating the output and recording mecha- 

 nisms, and resetting the condensers after each integration period. 



The operations are activated by electrical impulses fed alternately to Input 

 1 and Input 2 of the processing unit. The trains of impulses are generated by 

 the two photocells of the synchronous switch mounted on the shaft coupling. 

 Four impulses are generated by each photocell during each revolution of the 

 mechanism. Impulses can also be generated by a miniature synchronous motor 

 in conjunction with an analogous photocell arrangement or by means of manually 

 operated pushbuttons. The mini -synchronous motor is positioned inside the 

 processing unit and is used for integration of span-check signals after each 

 measuring run and for calibration. The pushbuttons are mainly used for check- 

 ing and adjusting but are also useful for special tests needing long integration- 

 times. 



Integration can be made using either of two different programs, designated 

 Oscil. and Const., the sequence of events of which is shown in Table 1 and Fig. 

 15. The only difference between the two programs is that the polarity of a sig- 

 nal integrated by means of the Oscil. program is negative for the first half and 

 positive for the second half of an integration period, whereas the polarity of a 

 signal integrated by means of the Const, program is the same during a whole in- 

 tegration period. In both cases, the integration period corresponds to one com- 

 plete revolution of the mechanism and hence to one period of the force signal. 

 The complete programs, however, use 1-1/4 periods, resulting in the start of 

 each integration period occurring n 2 later than the one preceding it. This 

 facilitates alternate elimination of sine and cosine force-components, when 



336 



